Conventional vehicles such as automobiles have various electronic controllers (ECUs) mounted thereon including, for example, a running-control apparatus, a light control apparatus, a door control apparatus, an air-conditioner control apparatus, a car navigation apparatus, and an audio control apparatus as on-vehicle apparatuses.
These on-vehicle apparatuses are communicatively coupled to each other through, for example, a controller area network (CAN) communications, thereby exchanging information among the on-vehicle apparatuses (refer to Japanese Laid-open Patent Publication No. 2009-267853, for example).
However, the conventional on-vehicle apparatuses each have individually set values of a voltage to stop the operation or the control. Therefore, the on-vehicle apparatus may be disabled from communicating with the other on-vehicle apparatuses when the battery voltage of the vehicle decreases.
In Japanese Laid-open Patent Publication No. 2009-267853, a technology has been developed where a low voltage range having low reliability is provided between a recommended minimum operation-voltage and an operation stop voltage. However, the objective of this setting is to identify a cause of inability to receive a normal signal from an on-vehicle apparatus. In addition, with the technology, an on-vehicle apparatus has to operate with the low voltage range having low reliability.
Furthermore, with the technology disclosed in Japanese Laid-open Patent Publication No. 2009-267853, a representative on-vehicle apparatus has to store therein information of the recommended minimum operation-voltage of other on-vehicle apparatuses and detect the on-vehicle apparatus having a voltage value smaller than the recommended minimum operation-voltage, leading to complicated control.